CN114441827A - Method for measuring current at low-voltage end of electric furnace transformer - Google Patents
Method for measuring current at low-voltage end of electric furnace transformer Download PDFInfo
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- CN114441827A CN114441827A CN202111577569.0A CN202111577569A CN114441827A CN 114441827 A CN114441827 A CN 114441827A CN 202111577569 A CN202111577569 A CN 202111577569A CN 114441827 A CN114441827 A CN 114441827A
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- 238000000034 method Methods 0.000 title claims abstract description 31
- 230000009466 transformation Effects 0.000 claims description 4
- 238000002955 isolation Methods 0.000 claims description 3
- 238000010079 rubber tapping Methods 0.000 claims description 2
- 230000007423 decrease Effects 0.000 description 5
- 238000003723 Smelting Methods 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 239000013064 chemical raw material Substances 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 238000005070 sampling Methods 0.000 description 1
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
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Abstract
The application discloses a method for measuring the current at the low-voltage end of an electric furnace transformer, which comprises the following steps: the method comprises the steps that a current collecting device for collecting current of a high-voltage end of an electric furnace transformer is arranged, the current measuring device comprises a high-voltage side sleeve mutual inductor and a first low-voltage current mutual inductor, a primary end of the high-voltage side sleeve mutual inductor is electrically connected with the high-voltage end, a secondary end of the high-voltage side sleeve mutual inductor is connected into a secondary turntable, an outlet of the secondary turntable is in multi-tap arrangement, and a primary end of the first low-voltage current mutual inductor is connected into an outlet of the secondary turntable; determining the current ratio of the high-voltage side sleeve transformer to the first low-voltage current transformer; measuring a high-voltage end line through the current measuring device to obtain a measured current value; and obtaining a low-voltage end current value according to a preset first current ratio and the measured current value. The method is equivalent to installing a current transformer on the low-voltage side, realizes the collection of the high current on the low-voltage side in the form of an electromagnetic transformer, and realizes the access to a relay protection system.
Description
Technical Field
The application relates to the technical field, in particular to a method for measuring the low-voltage end current of an electric furnace transformer.
Background
The electric furnace is important chemical raw material smelting equipment in China, the electric furnace transformer is a transformer for providing power supply for the electric furnace transformer, is the heart of the smelting equipment, and is very important for relay protection and very important for safety production along with higher requirements on safety production.
The electric furnace is characterized in that the current is very large and is often over 30000A, and the current transformer cannot be manufactured in such a large range due to process limitation, so that the current sampling of the electric furnace is generally realized by adopting a Rogowski coil. However, current output signals of the Rogowski coil are 4-20mA analog quantity, the relay protection device adopts a 5A system, the Rogowski coil cannot be directly connected to the relay protection device, only PLC and other equipment can be used for protection, and the difference between protection performances such as protection action time and the like is larger than that of the relay protection device.
Disclosure of Invention
In order to solve the technical problems, the following technical scheme is provided:
in a first aspect, an embodiment of the present application provides a method for measuring a low-voltage end current of an electric furnace transformer, where the method includes: the method comprises the steps that a current collecting device for collecting current of a high-voltage end of an electric furnace transformer is arranged, the current measuring device comprises a high-voltage side sleeve mutual inductor and a first low-voltage current mutual inductor, the primary end of the high-voltage side sleeve mutual inductor is electrically connected with the high-voltage end, the secondary end of the high-voltage side sleeve mutual inductor is connected into a secondary turntable, the outlet of the secondary turntable is in multi-tap arrangement, and the primary end of the first low-voltage current mutual inductor is connected into the outlet of the secondary turntable; determining the current ratio of the high-voltage side sleeve transformer to the first low-voltage current transformer; measuring a high-voltage end line through the current measuring device to obtain a measured current value; and obtaining a low-voltage end current value according to a preset first current ratio and the measured current value.
By adopting the implementation mode, the current transformer is equivalently arranged on the low-voltage side, the large current on the low-voltage side is acquired in the form of the electromagnetic transformer, and the relay protection system is accessed.
With reference to the first aspect, in a first possible implementation manner of the first aspect, the determining a current ratio between the high-side bushing transformer and the first low-voltage current transformer includes: obtaining the overload maximum current of the low-voltage side of the transformer; presetting a secondary end output current of a first low-voltage current transformer, and determining a first current ratio according to the secondary end output current of the first low-voltage current transformer and the low-voltage side overload maximum current; and respectively determining the rated current ratio of the high-voltage side sleeve transformer and the second current ratio of the first low-voltage current transformer according to the output current of the secondary end of the first low-voltage current transformer, wherein the second current ratio is changed according to different tap positions in rotary connection of the turntable.
With reference to the first possible implementation manner of the first aspect, in a second possible implementation manner of the first aspect, the current measuring device is configured to perform transformer parameter setting according to the rated current ratio and the second current, and the current at the high-voltage end of the electric furnace transformer is measured to obtain a measured current value.
With reference to the first or second possible implementation manner of the first aspect, in a third possible implementation manner of the first aspect, the obtaining of the maximum overload current on the low-voltage side of the transformer includes: calculating rated maximum low-voltage side current according to the secondary voltage of the transformer capacity; and obtaining the overload maximum current of the low-voltage side according to the historical average overload and the rated maximum low-voltage side current.
With reference to the first aspect, in a fourth possible implementation manner of the first aspect, the turntable is provided with a plurality of gears, the high-voltage end current corresponding to the low gear and the high gear gradually decreases, and the second current ratio also gradually decreases.
With reference to the first aspect or any one of the first to the fourth possible implementation manners of the first aspect, in a fifth possible implementation manner of the first aspect, a secondary end of the first low-voltage current transformer is connected to a primary end of a second low-voltage current transformer, a secondary end of the second low-voltage current transformer outputs a test current, a primary end input current and a secondary end output current of the second low-voltage current transformer are the same, and the second low-voltage current transformer is used for electrical isolation.
With reference to the fifth possible implementation manner of the first aspect, in a sixth possible implementation manner of the first aspect, the high-voltage side bushing transformer, the first low-voltage current transformer and the second low-voltage current transformer are all provided with three lines corresponding to different phases of a three-phase circuit.
With reference to the first aspect, in a seventh possible implementation manner of the first aspect, the primary ends of the first current transformers customize the same number of primary taps according to the number of tapping positions of the transformer, and the number-of-turns ratio is different according to different positions.
With reference to the fifth possible implementation manner of the first aspect, in an eighth possible implementation manner of the first aspect, the secondary end of the first current transformer is connected to the primary end of the second current transformer in an angle.
Drawings
Fig. 1 is a schematic flow chart of a method for measuring a low-voltage end current of an electric furnace transformer provided in an embodiment of the present application;
fig. 2 is a schematic structural diagram of a current collecting device according to an embodiment of the present application.
Detailed Description
The scheme is explained in the following by combining the attached drawings and the detailed description.
Fig. 1 is a schematic flow chart of a method for measuring a low-voltage end current of an electric furnace transformer provided in an embodiment of the present application, and referring to fig. 1, the method for measuring a low-voltage end current of an electric furnace transformer provided in the embodiment includes:
and S101, setting a current collecting device for collecting the current of the high-voltage end of the electric furnace transformer.
Referring to fig. 2, in this embodiment, the current measuring apparatus includes a high-voltage side bushing transformer CT1 and a first low-voltage current transformer, a primary end of the high-voltage side bushing transformer CT1 is electrically connected to a high-voltage end, a secondary end of the high-voltage side bushing transformer CT1 is connected to a secondary turntable, an outlet of the secondary turntable is provided with multiple taps, and a primary end of the first low-voltage current transformer is connected to an outlet of the secondary turntable.
Further, the rotating disc shown in fig. 2 is provided with 11 gears, the current at the high-voltage end gradually decreases from the 1 gear to the 11 gear, and the second current ratio also gradually decreases.
In this embodiment, the secondary terminal of the first low-voltage current transformer is connected to the primary terminal of the second low-voltage current transformer, the secondary terminal of the second low-voltage current transformer outputs the test current, the primary terminal input current and the secondary terminal output current of the second low-voltage current transformer are the same, and the second low-voltage current transformer is used for electrical isolation. The high-voltage side bushing transformer CT1, the first low-voltage current transformer and the second low-voltage current transformer are all provided with three lines corresponding to different phases of a three-phase circuit.
In this embodiment, the primary end of the first current transformer CT2 customizes the same number of primary taps according to the number of tap positions of the transformer, and the turns ratio is different according to different tap positions. In the operation process of the transformer, when the gear is adjusted, the tap access position of the first current transformer CT2 can be synchronously adjusted by the secondary turntable, the synchronization with the transformer is realized, the tap current transformation ratio of the first current transformer CT2 is calculated according to the turn ratio of the transformer, and the conversion of different current transformation ratios of the tap positions is perfectly realized. The secondary terminal of the first current transformer CT2 is connected to the primary terminal of the second current transformer CT 3. The outlet of the first transformer is connected with a second current transformer CT3, and is connected into Y connection or D connection according to the connection group of the transformer.
S102, determining the current ratio of the high-voltage side bushing transformer CT1 to the first low-voltage current transformer.
Obtaining the overload maximum current of the low-voltage side of the transformer, specifically, calculating the rated maximum low-voltage side current according to the secondary voltage of the transformer capacity; and obtaining the overload maximum current of the low-voltage side according to the historical average overload and the rated maximum low-voltage side current. Presetting the output current of the secondary end of the first low-voltage current transformer, and determining a first current ratio according to the output current of the secondary end of the first low-voltage current transformer and the overload maximum current of the low-voltage side.
One illustrative example: according to the secondary voltage of the transformer capacity, the rated maximum low-voltage side current is calculated to be 44446A, and the conventional overload reaches 20 percent due to the particularity of furnace change. After overload, the low-voltage side current is 53335A, the low-voltage side transformer theoretical transformation ratio 75000/5 is more appropriate, the current ratio is 15000, and then the first current ratio in the embodiment is 15000.
And respectively determining a rated current ratio of the high-voltage side bushing transformer CT1 and a second current ratio of the first low-voltage current transformer according to the output current of the secondary end of the first low-voltage current transformer, wherein the second current ratio is changed according to different tap positions of the rotary disc in rotary connection.
For an illustrative example, when the transformer is in 1 gear, if the rated current of the low-voltage side is 35883A and the current ratio is 15000, the needed transformer measures 2.392 (after angle connection) for the secondary value of the second current transformer CT3
According to the fact that the measured secondary current of the high-voltage side sleeve transformer CT1 is 1.65, the measured secondary current of the first current transformer CT2 is 1.381, 1.65/1.381 is calculated to be 1.195, and finally the current ratio of the first current transformer CT2 is determined to be 1.195.
And carrying out mutual inductor parameter setting on the current measuring device according to the rated current ratio and the second current, and measuring the current of the high-voltage end of the electric furnace transformer to obtain a measured current value.
And S103, measuring the high-voltage end line through the current measuring device to obtain a measured current value.
Table low voltage current values corresponding to different high voltage current values
The high side line is measured by the high side bushing transformer CT1 in the current measuring device, as shown in table one, which gives 8 measurements, where the second current ratio decreases from 1 st to 11 th due to the secondary turntable, so at high side current, the final output current obtained is rather small.
And S104, obtaining a low-voltage end current value according to a preset first current ratio and the measured current value.
Further referring to table 1, if the measured current value is 2.582A, the low-side small current value is 2.583a multiplied by the first current ratio 15000 equal to 38725A.
It is noted that, in this document, relational terms such as "first" and "second," and the like, may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other identical elements in a process, method, article, or apparatus that comprises the element.
Claims (9)
1. A method for measuring the current at the low-voltage end of an electric furnace transformer is characterized by comprising the following steps:
the method comprises the following steps of setting a current collecting device for collecting current of a high-voltage end of an electric furnace transformer, wherein the current measuring device comprises a high-voltage side sleeve mutual inductor and a first low-voltage current mutual inductor, a primary end of the high-voltage side sleeve mutual inductor is electrically connected with the high-voltage end, a secondary turntable is connected to a secondary end of the high-voltage side sleeve mutual inductor, the outlet of the secondary turntable is in multi-tap arrangement, a primary end of the first low-voltage current mutual inductor is connected to the outlet of the secondary turntable, and the method comprises the following steps:
determining the current ratio of the high-voltage side sleeve transformer to the first low-voltage current transformer;
measuring a high-voltage end line through the current measuring device to obtain a measured current value;
and obtaining a low-voltage end current value according to a preset first current ratio and the measured current value.
2. The method of measuring the current at the low voltage end of the electric furnace transformer of claim 1, wherein determining the current ratio of the high voltage side bushing transformer and the first low voltage current transformer comprises:
obtaining the overload maximum current of the low-voltage side of the transformer;
presetting secondary end output current of a first low-voltage current transformer, and determining a first current ratio according to the secondary end output current of the first low-voltage current transformer and low-voltage side overload maximum current;
and respectively determining the rated current ratio of the high-voltage side sleeve transformer and the second current ratio of the first low-voltage current transformer according to the output current of the secondary end of the first low-voltage current transformer, wherein the second current ratio is changed according to different tap positions in rotary connection of the turntable.
3. The electric furnace transformer low-voltage end current measuring method according to claim 2, wherein mutual inductor parameter setting is carried out on the current measuring device according to the rated current ratio and the second current, and the electric furnace transformer high-voltage end current is measured to obtain a measured current value.
4. The method for measuring the low-voltage end current of the electric furnace transformer as claimed in claim 2 or 3, wherein the step of obtaining the maximum overload current of the low-voltage side of the transformer comprises the following steps:
calculating rated maximum low-voltage side current according to the secondary voltage of the transformer capacity;
and obtaining the overload maximum current of the low-voltage side according to the historical average overload and the rated maximum low-voltage side current.
5. The electric furnace transformer low-voltage end current measuring method according to claim 1, wherein the rotating disc is provided with a plurality of gears, the high-voltage end current corresponding to the low gear is gradually reduced from the low gear to the high gear, and the second current ratio is also gradually reduced.
6. The method for measuring the low-voltage end current of the electric furnace transformer according to any one of claims 1 to 5, wherein the secondary end of the first low-voltage current transformer is connected with the primary end of a second low-voltage current transformer, the secondary end of the second low-voltage current transformer outputs a test current, the primary end input current and the secondary end output current of the second low-voltage current transformer are the same, and the second low-voltage current transformer is used for electrical isolation.
7. The method for measuring the low-voltage end current of the electric furnace transformer as claimed in claim 6, wherein the high-voltage side sleeve transformer, the first low-voltage current transformer and the second low-voltage current transformer are all provided in three numbers corresponding to different phase lines of a three-phase circuit.
8. The electric furnace transformer low-voltage end current measuring method according to claim 1, wherein the primary end of the first current transformer is provided with the same number of primary taps according to the number of tapping gears of the transformer, and the number of turns and the transformation ratio of the primary taps are different according to different gears.
9. The method for measuring the low-voltage end current of the electric furnace transformer as claimed in claim 6, wherein the secondary end of the first current transformer is in angular connection with the primary end of the second current transformer.
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| CN202111577569.0A CN114441827A (en) | 2021-12-22 | 2021-12-22 | Method for measuring current at low-voltage end of electric furnace transformer |
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| CN202111577569.0A CN114441827A (en) | 2021-12-22 | 2021-12-22 | Method for measuring current at low-voltage end of electric furnace transformer |
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